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'Patent e d Dec. '10. 1929 UNITED STATES were I PATENT OFFICE cam. N. m, rnomas w. 3mm, AYLMEB. n. "MAUDE, or Mano, wnsr vmemra, assreuons TO THE RUBBER snnvIoE Lama-moms 00., or mow,

' OHIO, A CORPORATION 01 OHIO Ho Drawing.

Our present invention is directed to improvements in the process of manufacturing acetaldehyde by a cyclic and substantially continuous process wherein acetylene is 5 passed through a heated acid solution carrying a reactlon catalyst suspended therein. The process will be understood from the following specification wherein the invention is fully set forth and described.

Various processes heretofore have been pro posed'for the reparation of aoetaldehyde from acetylene y the action of the latter on sulfuric or phosphoric acid solutions, containing solutions of various catalysts. However,

great difliculty has been experienced in the commercial operationof these earlier processe's. Furthermore, the recovery of the aldehyde from the reaction products by the condensation and refrigeration means ordinarily employed has been carried out only at great cost and is always accompanied withalosses of the aldehyde.

According to the present invention, it has been found that the manufacture of acetaldehyde can be commercially carried out with great ease andefiiciency by operating in a continuous manner, wherebya high yield of aldehyde is realized and the acetylene is transformed into the product desired with the generation of a minimum quantity of undesirable byiproducts. I

carrying out the process according to this invention, the reactlon vessel comprising an acid resist-antmaterial, or preferably of ordinary, construction, lined with some readily replaceable acid-resisting material,- is char ed with a quantity of sulfuric acid of esired strength, although a solution containing from 25 to acid ispreferably employed. -The acid also carries a quantity of a catalyst of the reaction taking plase. Al-

- though any suitable catalyst may be employed, we have found that a substance such as mercurous sulfate, that is but slightly soluble in the acid solution used, gives the most favorableresults. The proper proportion of catalyst that is required is more fully explained hereinafter.

Acetylene from any source'of supply and without any treatment other than the trap Application filed April 1.2, 1926 Serial No. 101,562.

ping out of any mechanically carried water A to avoid undue dilution of the acid, is passed under a pressure of approximately 10 pounds per square inch above atmospheric pressure through the acid-catalyst mixture at a rate of about 100 cubic feet per hour to every cubic foot of sulphuric acidmercurous sulphate mxtu're in the reaction vessel. The hydration of acetylene is an exothermic reaction, and although the reaction will proceed in a relatively cool li uid, the change takes place much more readily at higher temperatures,

for example from 68 to. 80 C. It is, then,

desirable when first starting the operation, to

introduce into the reaction vessel a sufficient quantlty of steam to heat the mixture to a temperature of approximately 68 C. The

uantity of acid employed, and the proportlon of catalyst taken, are so chosen that the heat evolved in the reaction will maintain the tem erature between the limits mentioned. If t e temperature begins to fall, it is an indication that the rate ofhydration of the acetylene is decreasing, whereupon a suflicient quantity of fresh catalyst is added to the acid solution. to bring the temperature back to I about C. Although the temperatures mentioned are not intended to indicate limits outside of which no reaction would take place, yet they have been found to comprise the most efficient range of temperature for the acid strength and catalyst particularly mentioned.

Operating under the conditions set forth, approximately 15% of acetaldehyde is produced by each passa' e of a given quantity of acetylene through t e reaction vessel. The

gas, carrying vapors of acetaldehyde, is

passed through a reflux condenser, functlonmg as a fractionating column, and cooled to ap roximately 40 and preferably lined wit some acid-resistant material, thence through a trap containing coke, unglazed brick or porcelain or other like material to remove any traces of acid mechanically carried by the \vapors, and then through a second condenser cooled by a stream of water to a temperature of approximately 21 to 30 (3., that is, slightly above the boiling poinif the acetaldehyde. Although all traces of acid I are ordinarily completely removed from the product by the means already described, it is desirable to pass the cooled mixture of vapors and gases from the second condenser through a second trap also filled with a bathing material, suchas coke, unglazed brick and the 1 (e.

The greatest obstacle in the way of the successful commercial production of acetaldehyde from acet lene has been the relatively high losses resulting from the attempted condensation and redistillation of the aldehyde vapors. This difliculty we avoid by passing the mixture of aldehyde and acetylene.v

through-a series of reaction vessels containing a material that will combine with the aldehyde, preferably by forming a condensation or addition product therewith, but which will not react with the acetylene. By this method of operating, the aldehyde is removed from the mixture and the acetylene is returned to the reaction vessel, preferably by a blower or other suitable means to be contacted again with the acid and catalyst, and.

thereby to produce a further quantity .of acetaldehyde. The method of separating the aldehyde from the acetylene is more specifically described and claimed in another Pat-- desirable from time .to time as necessity reent No. 1,696,479 filed by one of us on April It is found that as the formation of aldehyde proceeds from the acetylene, the acid solution in the reaction chamber becomes contaminated with an increasing quantity of polymerized materials and organic side-reaction products so that the reaction no longer proceeds in an e'fiicient manner. It is then,

quires, to withdraw the contents from the reaction vessel and charge again with fresh acid containing a quantity of catalyst as already described. The mercury containing material in the spent acid liquor is recovered therefrom, and converted into fresh catalyst by any satisfactory process. The replacement of the acid solution with a fresh charge ofacid has been found to be necessary only after from forty-eight to seventy-two of continuous operation.

From the foregoing description, it will be evident that the process is continuous in every hours proportion of polymerization or other reaction products.

It is to be understood that the foregoing I description is given by way of example only,

and that the invention is not limited to the inga stream of acetylene at a pressure substantially 10 pounds above-atmospheric pressure throu h said acid solution,adding to the acid a su cient quantity of mercurous sul phate to maintain. the temperature of the acid-catalyst mixture at from 68 to (1, removing entrained water and acid from the mixture of acetylene and acetaldehyde so obtained, separating the acetaldehyde from. the mixture of aldeh de and acety ene, and returning'the acety ene to the acid solution for further reaction therewith.

2. In the process according to claim .1, the

step comprising flowing the acetylene gas through the acid-catalyst mixture at approximately the rate of 10.0 cubic feet of acetylene per hour to each cubic foot of acid-catalyst mixture employed.

In testimony whereof we aflix our signatures.

' CARL N. HAND.

. THOMAS W. BARTRAM;

. AYLMER H.

v respect and may be carried out readily :5 and conveniently on a commercial scale, There is practically no loss of actylene and by means 4 of the method employed for the recovery .of the aldehyde produced, no appreciable loss of theproduct results andoonseeuently the aetylene is substantially complete y convert ed into aldehyde. Inasmuch asan excess of acetylene is passing through the reaction vessel, this is useful in eweepmg away from the reactionzoneall of the aldehyde produced, A

as qui k y as it is formed, and before it has time oropportunity to reduce any appreciable 

